The population figures do not reflect the practice of countries that report significantly different populations of citizens domestically and overall. Some countries, notably Thailand, do not report total population, exclusively counting citizens; for total populations an international agency must issue an estimate.[citation needed]

Because the compiled figures are not collected at the same time in every country, or at the same level of accuracy, the resulting numerical comparisons may create misleading conclusions. Furthermore, the addition of figures from all countries may not equal the world total. A handful of nations have not conducted a census in over 30 years, providing high error margin estimates only.